Heat exchanger

ABSTRACT

A heat exchanger for performing heat exchange of a medium by heat conducted to tubes ( 210 ) and fins ( 220 ), the heat exchanger is configured by assembling the tubes, the fins, tanks ( 300 ) and a connector ( 400 ) and heating them in a furnace to be brazed into one body, wherein the connector is made of aluminum or its alloy and has a seating face to be brazed to the outer surface of the tank, and when it is determined that the connector has a surface area of X [cm 2 ] and a volume of Y [cm 3 ], they have a relation of X≧1.5·(36πY 2 ) 1/3 , Y≦30.

TECHNICAL FIELD

The present invention relates to a heat exchanger which is comprised oftubes for flowing a medium, fins attached to the tubes, tanks to whichends of the tubes are connected, and connectors disposed on the tanks,and performs heat exchange of the medium by heat conducted to the tubesand the fins.

BACKGROUND ART

A heat exchanger such as a condenser of a refrigeration cycle or aradiator of automobiles is configured by alternately stacking aplurality of tubes and a plurality of fins to form a core and connectingends of the tubes to the tanks. A medium is introduced into the insidethrough one of connectors disposed on the tank, flowned through thetubes while performing heat exchange with heat conducted to the core,and discharged to the outside from the other connector disposed on thetank.

Generally, this type of heat exchanger is produced by assembling thetubes, fins, tanks and connectors and heating the assembly to braze intoone body in a furnace. And, to braze in the furnace, a brazing materialand flux are previously disposed on required potions of the respectivemembers.

To heat in the furnace, it is important that the respective members areheated as uniformly as possible so to braze the entire heat exchangeruniformly.

In this connection, the connectors have a disadvantage that heatconduction is quite slow and it takes time to braze as compared with thetubes and the fins which are formed to be thin.

The present invention was achieved in view of the above-describedcircumstances, and an object of the invention is to provide a heatexchanger which can have the connectors brazed efficiently.

DISCLOSURE OF THE INVENTION

The invention described in claim 1 is a heat exchanger which comprisestubes for flowing a medium, fins mounted on the tubes, tanks to whichthe ends of the tubes are connected and connectors disposed on thetanks, and performs heat exchange of the medium by heat conducted to thetubes and the fins, wherein the heat exchanger is formed by assemblingthe tubes, the fins, the tanks and the connectors and heating them in afurnace to braze into one body, the connectors are made of aluminum orits alloy and having a seating face to be brazed to the outer surface ofthe tanks, and when it is assumed that the connectors have a surfacearea of X [cm²] and a volume of Y [cm³], they are:X≧1.5·(36πY ²)^(1/3)  {circle around (1)}Y≦30  {circle around (2)}and, the connectors are brazed efficiently by configuring as describedabove. Its concept will be described below.

First, the connectors conduct heat very slowly as compared with thetubes and the fins which are formed thin, so that heat transmission isimproved by securing a large surface area against a volume.

Here, when it is assumed that a certain object has a surface area X anda volume Y, a shape having minimum X against Y is a sphere. And, when itis assumed that the sphere has a radius r, they are in the followingrelationship:X=4πr²  {circle around (3)}Y=4πr ³/3  {circle around (4)}when r is removed from the expressions {circle around (3)} and {circlearound (4)}, the result is:x=(36πY ²)^(1/3)  {circle around (5)}where, π is the ratio of the circumference of a circle to its diameter.

And, the present invention determines the surface areas of theconnectors to 1.5 times or more a sphere based on the surface area ofthe sphere having a volume equal to that of the connectors as astandard. Therefore, the surface area of the connector is 1.5 times ormore the right side of the expression {circle around (5)} and indicatedby the expression {circle around (1)}.

The upper limit of the volume of the connector is determined to be 30[cm³] as indicated by the expression {circle around (2)}. Specifically,the surface area is proportional to the square of the diameter, and thevolume is proportional to the cube of the diameter. Therefore, brazingof the connector becomes disadvantageous as its volume becomes larger.Thus, the volume of the connector is determined to have theabove-described upper limit to adequately secure the brazing property.

When it is assumed that one side of a cube is a, the surface area andthe volume have the following relationship:X=6a²  {circle around (6)}Y=a³  {circle around (7)},andwhen a is removed from the expressions {circle around (6)} and {circlearound (7)}, the result isX=6Y^(2/3)  {circle around (8)}.According to the expressions {circle around (5)} and {circle around(8)}, the surface area of the cube becomes approximately 1.24 times thatof a sphere having the same volume.

In addition, this type of conventional connector, namely a connectorhaving a seating face to be brazed to the outer surface of the tank,having a volume of 30 [cm³] or less, was sampled in plurality of types,and the samples were measured for a ratio of surface area against thoseof spheres having the same volumes. It was found that the ratios ofsurface area were somewhat larger than the above-described 1.24 times,namely approximately 1.3 to 1.45 times.

Specifically, the numerical value 1.5 times or more the expression{circle around (1)} is determined considering the conventionalconnector, and it falls in a range to improve the heat transmission ofthe connector without fail. And, such a numerical value is considered tobe more preferably 1.8 times or more.

FIG. 7 is a correlation graph of a surface area and a volume. In thedrawing, values of a surface area and a volume of the connectoraccording to the invention are indicated in a hatched area A.

The connector is provided with a pipe section which is protruded fromthe seating face for insertion into the tank.

By configuring as described above, the connector is accurately disposedby inserting the pipe section into the tank.

The connector is provided with a bolt-attaching section for screwing orinserting a bolt for connection of an outer passage.

By configuring as described above, the connector and the outer passageare connected with a bolt, and airtightness and support strength aresecured without fail.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view showing a heat exchanger according to anembodiment of the invention.

FIG. 2 is an exploded perspective view showing a tank and a coreaccording to the embodiment of the invention.

FIG. 3 is an explanatory diagram showing a tank and a connectoraccording to an embodiment of the invention.

FIG. 4 is a front perspective view showing an inlet connector accordingto an embodiment of the invention.

FIG. 5 is a rear perspective view showing the inlet connector accordingto the embodiment of the invention.

FIG. 6 is a perspective view showing a connector for connection of agas-liquid separator according to an embodiment of the invention.

FIG. 7 is a correlation graph of a surface area and a volume.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described in detail belowwith reference to the accompanying drawings.

A heat exchanger 1 of this embodiment is a radiator of a refrigerationcycle for car air conditioner mounted on automobiles and provided with acore 200 formed by alternately stacking a plurality of tubes 210 forflowing a medium (namely a refrigerant) and a plurality of fins 220 anda pair of tanks 300 to which both ends of the tubes 210 are connected asshown in FIG. 1 to perform heat exchange of the medium by heat conductedto the core 200.

Such a refrigeration cycle is to circulate a CFC-based medium andprovided with a compressor for compressing the medium, a radiator forcooling the compressed refrigerant, an expansion valve for decompressingthe cooled refrigerant, and an evaporator for evaporating thedecompressed refrigerant. Specifically, the heat exchanger 1 of thisembodiment as the radiator is a condenser which cools the medium andcondenses from a gas layer to a liquid layer.

The tanks 300 are provided with an inlet connector 400 for introducingthe medium and an outlet connector 500 for discharging the medium.

The medium is flowed into the tank 300 through the inlet connector 400,flowed through the tubes 210 while performing heat exchange anddischarged to the outside of the tank 300 through the outlet connector500.

The respective tanks 300 are divided their interiors at prescribedintervals, so that the medium is made to reciprocate a plurality oftimes between the tanks 300.

A side plate 600 is disposed as a reinforcing member on the top andbottom sides of the core 200. Ends of the respective side plates 600 aresupported by the tanks 300.

Besides, one of the tanks 300 is provided with a gas-liquid separator700. The medium, while flowing from the inlet connector 400 to theoutlet connector 500, is first sent from the tank 300 to the gas-liquidseparator 700 and only the liquid layer is sent to the outlet 500.

The tank 300 and the gas-liquid separator 700 are mutually connected viaa connector 800 for connection of the gas-liquid separator which isdisposed on the side of the tank 300.

The tubes 210, fins 220, tanks 300, inlet connector 400, outletconnector 500 and side plates 600 configuring the heat exchanger 1 areformed of aluminum or aluminum alloy, and such members are assembled andthe assembly is heated in a furnace to form one body. The brazingmaterial clad and flux are previously applied to the necessary portionsof the respective members.

Especially, the tubes 210 of this embodiment are formed to be flat byextrusion forming or roll forming of a plate. Their insides are dividedinto a plurality of sections in order to obtain the required pressureresistance.

The tanks 300 of this embodiment each is configured by assembling a tankplate 310 and an end plate 320 as shown in FIG. 2.

The tank plate 310 and the end plate 320 are formed by press-forming aplate of aluminum or aluminum alloy having a prescribed thickness.

The tank plate 310 is a semicircular cylindrical member, and the endplate 320 is a member provided with holes 321 into which the ends of thetubes 210 are inserted for connection. The holes 321 of the end plate320 are disposed in plural numbers at prescribed intervals along thelongitudinal direction of the end plate 320.

Partition plates 330 are disposed between the tank plate 310 and the endplate 320 with prescribed intervals. Specifically, the ends and interiorof the tank 300 are closed and divided by the partition plates 330.

In this embodiment, the tank plate 310 and the end plate 320 areassembled with the end plate 320 fitted to both edges of the tank plate310. And, both edges of the end plate 320 are brazed to the innerperiphery of the tank plate 310.

Besides, edges 310 a of the tank plate 310 are formed a plurality ofbending pieces 311 for holding the end plate 320 with appropriateintervals.

The end plate 320 is positioned on the tank plate 310 and fixed bybending the bending pieces 311. The bending pieces 311 are bent by acaulking jig or the like.

The inlet connector 400 is a block-shaped member which is formed bymachining aluminum or its alloy into a prescribed shape and has a pipesection 410 which is inserted into the tank plate 310, a curved seatingface 420 which is fitted to the outer surface of the tank plate 310, aconnection section 430 for connecting an outer passage, and a boltfitting portion 440 for screwing or inserting a bolt for connection ofthe outer passage as shown in FIG. 3 to FIG. 5. The pipe section 410 isprotruded from the seating face 420.

And, the inlet connector 400 is disposed by inserting the pipe section410 into the hole 312 formed in a required portion of the tank plate310, brazing the pipe section 410 to the hole 312 and brazing theseating face 420 to the outer surface of the tank plate 310.

The pipe section 410, which is inserted into the hole 312 of the tankplate 310, has its leading end partly expanded. By expanding the leadingend of the pipe section 410, the pipe section 410 is prevented fromcoming out, and the medium is flowed smoothly.

The tank plate 310 and the end plate 320 are assembled after insertingthe pipe section 410 of the connector 400 into the tank plate 310.

In this embodiment, the inlet connector 400 has a surface area of 35[cm²] and a volume of 5.5 [cm³]. And, aluminum or its alloy have aspecific gravity of approximately 2.7 [g/cm³], and the connector 400weighs approximately 15 [g].

And, when the connector 400 is determined to have a surface area of X[cm²] and a volume of Y [cm³],

-   -   1.5·(36πY²)^(1/3)≈22.6,    -   X≧1.5·(36πY²)^(l/3), and    -   Y≦30 is established.

Therefore, the inlet connector 400 can be brazed efficiently by brazingin a furnace.

The relationship between the surface area and the volume depends on thestructure, appearance and design of the connector 400, and the connector400 is designed based on such a configuration.

On the other hand, the outlet connector 500 has a surface area of 21[cm²] and a volume of 3.1 [cm³]. And, the connector 500 weighsapproximately 8.4 [g]. The other structure is the same as the inletconnector 400 and, therefore, its description is omitted.

When it is determined that the connector 500 has a surface area of X[cm²] and a volume of Y [cm³],

-   -   1.5·(36πY²)^(1/3)≈15.4,    -   X≧1.5·(36πY²)^(1/3), and    -   Y≦30 is established.

Therefore, the outlet connector 500 can also be brazed efficiently bybrazing in a furnace.

Besides, a connector 800 for connection of a gas-liquid separator ofthis embodiment is a block member formed by machining aluminum or itsalloy into a prescribed shape and has one passage for flowing the mediumfrom the tank 300 to the gas-liquid separator 700 and the other passagefor flowing the medium from the gas-liquid separator 700 to the tank300.

Specifically, the connector 800 has a seating face 820 which is brazedto the outer surface of the tank 300, a first pipe section 811 which isprotruded from the seating face 820 to provide an inlet end of onepassage into the tank 300, and a second pipe section 812 which isprotruded from the seating face 820 to provide an outlet end of theother passage into the tank 300 as shown in FIG. 6.

The brazing area between the seating face 820 and the tank 300 iswidened by flanges 821 formed on the required portions of the connector800.

The tank plate 310 is formed with holes into which the first pipesection 811 and the second pipe section 812 are inserted.

Specifically, the connector 800 for connection of the gas-liquidseparator has the first pipe section 811 and the second pipe section 812protruded from the seating face 820 and inserted into the holes of thetank plate 310, the first pipe section 811 and the second pipe section812 brazed to the holes by brazing in a furnace, and the seating face820 brazed to the outer surface of the tank 300 to secure airtightnesswith the tank 300 and a supporting strength to the tank 300.

Besides, one of the above-described partition plates 330 is disposedbetween the hole into which the first pipe section 811 is inserted andthe hole into which the second pipe section 812 is inserted in the tank300.

And, this connector 800 is provided with a bolt attaching section 840for insertion of a bolt, and the gas-liquid separator 700 is formed witha female thread section for screwing the bolt. The gas-liquid separator700 is attached by screwing the bolt which is inserted into the boltattaching section 840 into the female thread section.

When the gas-liquid separator 700 is attached, the outlet end of onepassage is connected to the inlet section of the gas-liquid separator700 through a third pipe section 831, the inlet end section of the otherpassage is connected to the outlet section of the gas-liquid separator700 through a fourth pipe section 832.

The connector 800 for connection of the gas-liquid separator has asurface area of 60 [cm²] and a volume of 15.6 [cm³]. And, the connector800 weighs approximately 42 [g].

When the connector 800 has a surface area of X [cm²] and a volume of Y[cm³],

-   -   1.5·(36πY²)^(1/3)≈45.3,    -   X≧1.5·(36πY²)^(1/3), and    -   Y≦30 is established.

Therefore, the connector 800 for connection of the gas-liquid separatorcan be brazed efficiently by brazing in a furnace.

The relationship between the surface area and the volume depends on thestructure, appearance and design of the connector 800, and the connector800 is also designed based on the above configuration.

As described above, in the heat exchanger of this embodiment, the inletconnector 400, the outlet connector 500 and the connector 800 forconnection of the gas-liquid separator can be efficiently brazed to thetanks 300, and a rationalization of its production was achieved.

The heat exchanger 1 of the embodiment is a condenser for condensing themedium from a gas layer to a liquid layer, and the structures of theinlet connector and the outlet connector can also be applied to, forexample, an evaporator, a radiator and another heat exchanger.

Especially, there is a refrigeration cycle adopting CO₂ as a medium inrecent years, and its radiator's inside pressure exceeds the criticalpoint of the medium depending on the use conditions such as atemperature. The critical point is a limit of a high temperature withthe coexistence of the liquid layer and the gas layer, namely, of thelimit on the side of high pressure.

And, when used as a radiator of such a refrigeration cycle, the innerpressure becomes very high, and, therefore a compressive strength ofeach member is improved by decreasing a passage area of the tanks ortubes for the refrigerant or increasing the thickness of the tank plateand the end plate.

The heat exchanger of this embodiment is preferably used for a radiatorof such a refrigeration cycle.

INDUSTRIAL APPLICABILITY

The present invention is a heat exchanger generally used for arefrigeration cycle of a car or home air conditioner, and especiallysuitable for a refrigeration cycle which uses, for example, CO₂ as arefrigerant and having a pressure in the radiator exceeding the criticalpoint of the refrigerant.

1. A heat exchanger which comprises tubes for flowing a medium, finsmounted on the tubes, tanks to which the ends of the tubes are connectedand connectors disposed on the tanks, and performs heat exchange of themedium by heat conducted to the tubes and the fins, wherein: the heatexchanger is formed by assembling the tubes, the fins, the tanks and theconnectors and heating them in a furnace to braze into one body, theconnectors are made of aluminum or its alloy and have a seating face tobe brazed to the outer surface of the tanks, and the connectors have asurface area of X as measured in cm² and a volume of Y as measured incm³, where X≧1.5·(36πY²)^(1/3), and Y≦30.
 2. The heat exchangeraccording to claim 1, wherein the connector is provided with a pipesection which is protruded from the seating face for insertion into thetank.
 3. The heat exchanger according to claim 1, wherein the connectoris provided with a bolt attaching section for screwing or inserting abolt for connecting of an outer passage.
 4. The heat exchanger accordingto claim 2, wherein the connector is provided with a bolt attachingsection for screwing or inserting a bolt for connecting of an outerpassage.